The present disclosure relates generally to a method for adjusting a natural refrigeration cycle rate of an air conditioning system.
Vehicle air conditioning systems provide comfort to vehicle passengers. Such systems include at least a compressor, a condenser, and an evaporator. Air conditioning systems often include an expansion valve, and the expansion valve may be thermostatically controlled in some systems. Generally, a compressor compresses a refrigerant, which is subsequently passed through a condenser and an expansion valve. As the refrigerant expands to a lower pressure across the expansion valve, it becomes colder. The cold refrigerant is passed through a heat exchanger generally known as an evaporator which cools air passed over it. If the temperature of the evaporator is below the Dew Point, water from the air will condense on the surface of the evaporator, thus lowering the humidity of the air. Generally, the operating temperature of the evaporator is regulated in order to prevent the freezing of moisture that collects thereon. The refrigeration can be stopped and restarted to regulate the temperature of the evaporator.
The refrigeration can be stopped and started in many ways, for example by controlling the compressor, the Thermostatic Expansion Valve (TXV), or combinations thereof. The compressor is often driven by a mechanical component that may be cycled “on” and “off”. For example, the mechanical component may be an electromagnetic clutch that can be used to releaseably couple the compressor to a pulley caused to rotate by a drive-belt connected to an engine. In another example, a variable displacement compressor may be configured to substantially stop compressing refrigerant. If there is a TXV, it may be cycled open and closed. The refrigeration cycle of the air conditioning system is managed, for example, using temperature or pressure relationships of the refrigeration circuit or of the evaporator in order to prevent the previously mentioned freezing conditions.
Temperature sensors may also be included to assist in managing the refrigeration cycles. Generally, temperature thresholds are used to regulate refrigeration cycles. For example if the temperature of air discharged from the evaporator exceeds an “on” threshold, the refrigeration cycle is activated by, for example, engaging the compressor or opening the TXV. If the temperature of air discharged from the evaporator falls below an “off” threshold, the refrigeration cycle is deactivated by, for example, disengaging the compressor or closing the TXV. In addition to or as an alternative to measuring the air temperature, the temperature of the fin and/or the refrigerant may be measured, and each of these measurements is indicative of the evaporator temperature.
The natural refrigeration cycle rate of an air conditioner is based on the rate at which the evaporator cools when cold refrigerant is supplied to it, and warms when the cold refrigerant supply is stopped.